VINE MILDEW. 119 



fructification discovered by Amici, when vve described the species, 

 it will be right to add a few words. 



It appears that the organs which we had taken at first for spores, 

 and which we found successively at the extremity of the erect 

 threads of the Oidium, are merely a sort of buds which, ger- 

 minating like true spores, are enabled in their absence to propagate 

 the species. In fact, at the end of 1851, Amici found on gourds 

 a form of fruit which was not even then * known in Erysiphe, 

 where it has since been detected. This fruit, named Sporangium 

 by Amici, Pycnidium by Tulasne, according to the different point 

 of view in which they regard it, is formed in the joints of the 

 necklaces of the fertile threads which swell, become yellow, 

 assume a cellular structure, that is cease to be continuous and 

 anhistous, and finally generate in their cavity many hundreds of 

 exceedingly small ovoid slightly reniform spores presenting a 

 little nucleus at either extremity. They have been observed 

 to germinate. Baron Cesati, who has also detected them in 

 Lombardy, thought that they authorised the creation of a new 

 genus. In a recent letter, Mr. Berkeley informs me that he has 

 detected them in grapes from Madeira.f Hitherto sporangia or 

 pycnidia had been found only in the southern parts of Europe. 

 Tulasne, however, in a recent communication to the Academy, 

 informs us that he has detected them near Paris, where they bad 

 not been previously observed. 



Even before the researches of Tulasne, an account of which 

 must now be given to complete the history of the Oidium, this 

 production had already received different names. M. Crocq,]: 

 although he confesses that he is not acquainted with Fries' 

 Systema My color/ ica, and had not seen any Oidium except that of 

 the vine, regards it, nevertheless, on very iu sufficient and con- 

 testable grounds, for he had never seen the sporangia, as worthy 

 to be raised to the rank of a genus under the name of Eudogenium, 

 Ehrenberg, to whom the fructification had been communicated 

 by Amici, considered it the type of a new genus, and gave it the 



* Dr. Plomley first detected it in the hop mildew in England almost at 

 the same time. See Gardeners' Chronicle, 1851, p. 5S2. 



+ There is some mistake about this. A peculiar production was found 

 in specimens of diseased grapes and vine-leaves from Madeira and the 

 upper and lower Corgo, wliich has been figured under the name of Coni- 

 sporium commilitans in the last part of this jom-nal, p. 58, fig. 9. — Tr. 



J Memou- on the vine mildew which obtained the especial approbation 

 of the Academy of Brussels, p. 15. 



